Bioswale at the SPICE Home shopping centre parking lot

The conventional collection and conveyance of stormwater runoff was not possible due to the limited capacity of the current urban drainage system. In the green part of the development plot, downstream from the parking lot, a bioswale was constructed. It offers multiple functions: stormwater runoff attenuation before restricted discharge into sewer network, groundwater recharge, stormwater treatment by plants and soil, landscaping function, space for snow storage during winter.
The bioswale is located at the side of the parking lot, from which stormwater is conveyed via surface runoff (sheet flow). The stormwater enters the bioswale via openings in the curbstones. The bioswale is implemented as an artificial depression with depth up to 50cm, filled with structured soil designed to provide better water treatment as well as a mix of plants tolerant to short periods of flooding. Most of the accumulated stormwater is treated by the plants and soil and infiltrates. In the event of extreme rain, an overflow with a limited discharge of at most 5 l/s is provided to the municipal stormwater sewer.
The main stakeholders are both the shopping centre/owner and the municipality. As this is a new practice, that contradicts some conventional rules, the municipality had to find the way to allow building this good practice by flexible interpretation of the building code. Also, this practice noted a necessity to amend the local regulation in order to facilitate more of such green features.